54 THE OCEAN WORLD. 
while that from the Arctic is so feeble as scarcely to be felt in 50° 
north, is indication enough as to the difference in degree of aérial 
rarefaction over the two regions. The significance of the fact is 
enhanced by the consideration that the ‘brave west winds,’ which 
are bound to the place of greatest rarefaction, rush more violently 
and constantly along to their destination than do the counter trades 
of the northern hemisphere. Why should these polar-bound winds 
differ so much in strength and prevalence, unless there be a much 
more abundant supply of caloric, and, consequently, a higher degree 
of rarefaction, at one pole than at the other ?” 
That this is the case is confirmed by all the known barometrical 
observations, which are very much lower in the Antarctic than in the 
Arctic, and Dr. Maury thinks this is doubtless due to the excess in 
the Antarctic regions of aqueous vapour and of latent heat. 
“There is,” he writes, “rarefaction in the Arctic regions. The 
winds show it, the barometer attests it, and the fact is consistent 
with the Russian theory of a Polynia in polar waters. Within the 
Antarctic Cirele, on the contrary, the winds bring air which has come 
over the water for the distance of hundreds of leagues all around ; 
consequently, a large portion of atmospheric air is driven away from 
the austral regions by the force of vapour.” 
